Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] drm/msm: NULL pointer dereference in get_pages() on dma_map_sgtable() error - [High] drm/msm/gem: dma_map_sgtable() maps via iommu-dma when ddev->dev has iommus --
commit 4102c003f615c93e1ee62bff745ef3edfcbebd16 Author: Rob Clark <[email protected]> drm/msm/gem: dma_map/unmap_sgtable() This commit replaces the cache sync helpers in msm_gem with unconditional dma_map_sgtable() and dma_unmap_sgtable() calls in get_pages() and put_pages() to populate scatterlist dma addresses and lengths. It also adds sgtable cleanup to the error path in get_pages(). > diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c > index 181b9ad326729..c97395e4ea2be 100644 > --- a/drivers/gpu/drm/msm/msm_gem.c > +++ b/drivers/gpu/drm/msm/msm_gem.c [ ... ] > @@ -219,13 +192,20 @@ static struct page **get_pages(struct drm_gem_object > *obj) > goto error; > } > > - update_device_mem(dev->dev_private, obj->size); > - > - /* For non-cached buffers, ensure the new pages are clean > - * because display controller, GPU, etc. are not coherent: > - */ > + /* For non-cached buffers, ensure the new pages are clean. */ > if (msm_obj->flags & MSM_BO_WC) > - sync_for_device(msm_obj); > + map_attrs = 0; > + > + ret = dma_map_sgtable(drm_dev_dma_dev(obj->dev), > + msm_obj->sgt, > + DMA_BIDIRECTIONAL, > + map_attrs); [Severity: High] Does calling dma_map_sgtable() on drm_dev_dma_dev(obj->dev) always take the dma-direct path when dma_map_ops is null? In kernel/dma/mapping.c:dma_go_direct(), use_dma_iommu(dev) is checked before testing whether ops is null: kernel/dma/mapping.c:dma_go_direct() { if (use_dma_iommu(dev)) return false; if (likely(!ops)) return true; ... } On platforms where the iommus property in device tree is attached directly to the mdp device (obj->dev->dev) rather than the parent mdss node (as handled in drivers/gpu/drm/msm/msm_kms.c:msm_kms_init_vm() when checking device_iommu_mapped(mdp_dev)), such as qcom_iommu platforms (msm8916, msm8939, msm8953, etc.) and qcom,mdp5 arm-smmu-qcom platforms (msm8996, sdm630, sdm660) that are not matched in qcom_smmu_client_of_match[], the iommu core allocates a default dma domain and sets DEV_FLAG_DMA_IOMMU on obj->dev->dev. When msm_iommu_new() later attaches an unmanaged domain via iommu_attach_device(), DEV_FLAG_DMA_IOMMU and group->default_domain remain on the device. As a result, get_pages() -> dma_map_sgtable() -> __dma_map_sg_attrs() -> iommu_dma_map_sg() maps every buffer into the unused default_domain and populates sg_dma_address(sg) with default_domain dma addresses instead of physical addresses. When paired with the subsequent change in this series ("drm/msm: Convert map helper to use dma-address") where __do_map() passes sg_dma_address(sg) as the physical address to pgtable->map(), won't this program the gpu and display page tables with default_domain dma addresses instead of cpu physical addresses on those platforms? > + if (ret) { > + DRM_DEV_ERROR(dev->dev, "could not map sgtable: %d\n", > ret); > + goto error; > + } > + > + update_device_mem(dev->dev_private, obj->size); > > update_lru(obj); > } > @@ -233,6 +213,8 @@ static struct page **get_pages(struct drm_gem_object *obj) > return msm_obj->pages; > > error: > + if (!IS_ERR(msm_obj->sgt)) > + drm_prime_gem_destroy(obj, msm_obj->sgt); [Severity: High] Will calling drm_prime_gem_destroy() in the get_pages() error path cause a null pointer dereference and leak msm_obj->sgt when dma_map_sgtable() fails? At the start of drivers/gpu/drm/msm/msm_gem.c:get_pages(), imported objects are rejected: if (drm_WARN_ON_ONCE(obj->dev, drm_gem_is_imported(obj))) return ERR_PTR(-EINVAL); so obj->import_attach is always null here, and msm_obj->sgt is allocated via drm_prime_pages_to_sg(). If dma_map_sgtable() fails and jumps to error, drm_prime_gem_destroy() is called with a valid msm_obj->sgt pointer on a non-imported object: drivers/gpu/drm/drm_prime.c:drm_prime_gem_destroy() { struct dma_buf_attachment *attach; struct dma_buf *dma_buf; attach = obj->import_attach; if (sg) dma_buf_unmap_attachment_unlocked(attach, sg, DMA_BIDIRECTIONAL); dma_buf = attach->dmabuf; ... } Since attach is null, dma_buf_unmap_attachment_unlocked() triggers a warning and attach->dmabuf dereferences a null pointer while leaving msm_obj->sgt unfreed. Should this error path free msm_obj->sgt using sg_free_table() and kfree() as done in put_pages()? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=2
